1. Field of the Invention
The present invention relates to information recording devices, information playback devices, information recording methods, information playback methods, and information recording media and program providing media used therewith. In particular, the present invention relates to an information recording device, an information playback device, an information recording method, and an information playback method in which, by using tree-structure, hierarchical key distribution to reduce the number of messages, reductions can be achieved in a data distribution load which is generated when a key such as master key or media key is updated, and in which two recording modes in connection with content-copy control, namely, a cognizant mode and a non-cognizant mode are clearly distinguished and separately performed, and to an information recording medium and a program providing medium which are used therewith.
Specifically, the present invention provides a construction which separately perform information recording in accordance with a cognizant mode which analyzes embedded copy control information in a data part of a packet having a header part and the data part, and information recording in accordance with a non-cognizant mode which does not analyze the embedded copy control information. The present invention relates to an information recording device, an information playback device, an information recording method, and an information playback method in which, by setting a content-encryption key for the information recording in accordance with the cognizant mode and a content-encryption key for the information recording in accordance with the non-cognizant mode so that the content-encryption key differ from each other, the two type of information recording are clearly distinguished and separately executed. The present invention also relates to an information recording medium and a program providing medium which are used with the information recording device, the information playback device, the information recording method, and the information playback method.
2. Description of the Related Art
With the progress and development in digital signal processing technology, the use of recording devices and recording media for digital data recording has become widespread in recent years. By using the recording devices and recording media, images and sound can be recorded and played back repeatedly without a deterioration in quality. In this manner, digital data can be repeatedly copied, while maintaining image and sound quality. Accordingly, if illegally copied recording media are distributed in the market, the profits to copyright holders for various type contents, such as music and movies, or appropriate dealership owners decrease. Nowadays, to prevent such unauthorized copying of digital data, various mechanisms (systems) are being incorporated into digital recording devices and recording media.
By way of example, the Serial Copy Management System (SCMS) is employed in Minidisk (MD) (trademark) devices as a method of preventing unauthorized copying. In the SCMS, a data playback side outputs an SCMS signal with audio data from a digital interface, and the data recording side controls, based on the SCMS signal, recording of the audio data from the data playback side so that unauthorized copying can be prevented.
Specifically, the SCMS signal represents an audio data type among “Copy Free” type in which the audio data may be copied any number of times, “Copy Once Allowed” type in which copying the audio data can be performed only once, and “Copy Prohibited” type in which the copying of the audio data is prohibited. When receiving the audio data from the digital interface, the data recording side detects the SCMS signal which is transmitted with the audio data. When the SCMS signal received represents the Copy Free type, the data recording side records the audio data on the Minidisk with the SCMS signal. When the SCMS signal represents the Copy Once Allowed type, the data recording side records the audio data on the Minidisk after changing the type of the audio data to the Copy Prohibited type. When the SCMS signal represents the Copy Prohibited type, the data recording side does not record the audio data. By using SCMS control, the Minidisk device prevents copyrighted audio data from being illegally copied.
However, it is difficult for the SCMS to cope with a case in which a Minidisk device having no mechanism for performing SCMS control is produced because the SCMS is based on the condition that a data recording device itself must have the above structure for performing control based on an SCMS signal of the recording of audio data from the playback side. Accordingly, for example, digital versatile disk (DVD) players use a content scramble system to prevent copyrighted data from being illegally copied.
In the content scramble system, video data, audio data, etc., are recorded in a DVD-ROM in encrypted form, and a key (decryption key) for decrypting the encrypted data is given to a licensed DVD player. The license is given to a DVD player designed to obey predetermined operation rules such as not performing unauthorized copying. Accordingly, the licensed DVD player can play back images and sound from the DVD-ROM by using the given key to decrypt the encrypted data in the DVD-ROM.
Conversely, an unlicensed DVD player cannot decrypt the encrypted data in the DVD-ROM because it does not have the key for decrypting the encrypted data. In the scramble system, a DVD player that does not meet the conditions required for licensing is not allowed to play back a DVD-ROM containing digital data, thereby preventing unauthorized copying.
In each content, whether or not the content can be copied under what conditions is designated beforehand by a content provider. Accordingly, in network connection, the designated conditions must be correctly posted from a device to another device. In the DTCP system, a method using copy control information is used to solve this problem. Concerning copy control information, there are two types of transmission techniques in accordance with device performance.
“Encryption Mode Indicator (EMI)” is a mechanism in which the two upper Sy bits in a packet header are used to send copy control information. By using this mechanism, a receiver device can easily perform accessing, and a content can be securely sent because the value of the Encryption Mode Indicator acts on a key for encrypting the content.
The Encryption Mode Indicator is used to indicate the encryption mode of the packet, and the generation modes of content encryption and decryption keys are designated. By disposing the Encryption Mode Indicator in an IEEE 1394 packet header, a receiver device is allowed to easily know the type of a mode for encryption of the content, for example, without extracting an embedded copy control information (described later) in an MPEG transport stream.
The 2-bit EMI information defines a different type of treatment in accordance with the set value. Specifically, value “00” is “Copy Free” indicating that neither authentication nor encryption is not required and that a content can be freely copied. Value “01” is “Copy One Generation” indicating that 1-generation copying is allowed. Value “10” is “No More Copies” indicating that re-copying after the above Copy One Generation is recorded once is inhibited. Value “11” is “Never Copy” indicating that a content is inhibited from being copied when being released.
Conversely, in a format (e.g., DV-format) in which an area for sending copy control information is reserved, the copy control information can be sent as part of a content. Copy control information that is embedded as part of the content, as described above, is called “embedded copy control information”. Normally, when a content is encrypted and transferred, embedded copy control information is similarly encrypted and transferred. It is considered that an intentional change of the embedded copy control information is difficult.
Here, in the case of a content having both the above 2-bit EMI copy control information and the embedded copy control information, a recording device that performs content recording updates the two types of copy control information, namely, both the Encryption Mode Indicator and the embedded copy control information. However, in the case of a recording device that does not have ability to analyze the embedded copy control information, the Encryption Mode Indicator is updated but the embedded copy control information is not updated.
A recording technique in which in a content recording mode, after updating embedded copy control information transmitted as part of a content, a recording device records the content with the updated embedded copy control information, is called a “cognizant mode”. In comparison between the cognizant mode and the non-cognizant mode, the non-cognizant mode causes a small load and can be easier employed because the updating of the embedded copy control information does not need to be performed. However, the DTCP has a rule in which in order that a device may perform MPEG decoding of a content and may output a video signal from an analog terminal, the device must employ the cognizant mode. Accordingly, a device having a decoding/display function must have a function of executing the cognizant mode.
Accordingly, it is possible that a content recording device execute the cognizant mode for a specified data format or implementing a specified function, and executes the non-cognizant mode for recording a content having a different data format.
As described above, in circumstances in which two type of copy control information, namely, Encryption Mode Indicator and embedded copy control information exist, and both a device that executes the cognizant mode and a device that executes the non-cognizant mode exit, it is preferable to distinguish between a content recorded in the cognizant mode and a communication network recorded in the non-cognizant mode.
In other words, when the cognizant mode is used to perform content recording, both types of copy control information, namely, Encryption Mode Indicator and embedded copy control information are updated, but when the non-cognizant mode is used to perform content recording, only Encryption Mode Indicator is updated and embedded copy control information is not updated. As a result, mismatching occurs between the Encryption Mode Indicator and the embedded copy control information recorded on a recording medium, and the mismatched Encryption Mode Indicator and embedded copy control information mix to cause confusion. That is why the distinction of the contents is preferable. Therefore, in order to prevent the two types of copy control information from being mismatched, for the content recorded in the cognizant mode, cognizant-mode recording/playback processing must be executed, and for the content recorded in the non-cognizant mode, non-cognizant-mode recording/playback processing must be executed.
Accordingly, one idea is that the cognizant mode and the non-cognizant mode are treated as separate recording modes. In this case, in order for a device to selectively execute both modes, the device must have processing configurations for executing both modes. This causes a problem in that the cost of the device is increased.